JEE Main 2021 · ChemistryNumerical answerNumerical valueMediumMulti-step

JEE Main 22 July 2021, Shift 2, Chemistry Q59

Question 59 of 90 in this shift, Chemistry question 29 of 30, Section B.

The number of acyclic structural isomers (including geometrical isomers) for pentene are ________.

Official answer

NTA final key.

Chapter: Hydrocarbons
Topic: Structural Isomerism
Idea tested: Enumeration of Structural Isomers

Same idea in other shifts

Asked 5× in all

2 Apr 2026, Shift 1 · Q72Consider the isomers of hydrocarbon with molecular formula $\mathrm{C_5H_{10}}$ . These isomers do not decolourise $\mathrm{KMnO_4}$ …HardNumerical value
4 Apr 2024, Shift 1 · Q88The number of different chain isomers for $\mathrm{C_7H_{16}}$ is ________.MediumNumerical value
25 Jul 2022, Shift 2 · Q90The total number of monobromo derivatives formed by the alkanes with molecular formula $\mathrm{C_5H_{12}}$ is (excluding stereo isomers)…MediumNumerical value
30 Jul 2022, Shift 2 · Q59The number of isomeric compounds (structural isomers only) possible with the molecular formula $\mathrm{C_5H_{10}O_2}$ , which do not react…HardNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.